The present invention generally relates to wireless switches, and more particularly to a wireless switch such as for use in an automobile or aircraft environment which does require a separate source of electrical power and associated wiring.
During the last decade, the automotive industry has experienced very significant growth in the electrical/electronic content of automobiles. The future growth rate of this content is predicted to become exponential. One cause for this significant growth is the availability of new vehicle systems such as cabin communication systems (CCS), active noise control systems, automobile personal computers, and on-board navigational systems. When any of these systems is added to a vehicle, interconnection is made using extensions of the vehicle""s conventional wiring/electrical distribution system technology. This conventional technology is characterized by very complex arrays of wire harnesses, interconnecting switches, motors, relays, electronic modules and the like. The proliferation in the quantity of the components required to implement new features is becoming difficult to manage from cost, serviceability and packaging viewpoints.
For the past thirty years, multiplexing has been extolled as a technology capable of addressing these issues. However, to date, no major automotive program has received large benefits from this technology. Significant reasons include the continued need for complex wire harness arrays to interconnect switches and sensors with multiplexed electronic modules and multiple power distribution feeds.
As shown in FIG. 1, conventional automotive control and electrical power distribution systems share a common architecture. Low power input signals from remotely located switches 10 are transmitted through wires 12 to a controller 14. Controller 14 typically includes a control algorithm for selectively distributing power to activate remotely located external loads 16 via additional wires 18. The necessity of supplying power from a vehicle battery 20 to each of the switches, controller, and loads generally results in a very complex electrical distribution system. As the number of systems on a vehicle increase, the complexity of the distribution as well as the bulk of associated wiring harnesses increases.
As a result, wireless communication between switches and controllers has been proposed as a way of reducing the number of wires. However, the need to supply electrical power still requires the use of a wiring harness, thereby negating much of the advantage gained by using a wireless communication system. In other words, a maximum reduction in the number of wires to zero will not be achieved, while full freedom to locate a switch anywhere in the vehicle will not be attained.
The use of a dedicated battery to provide power locally at individual switches can eliminate the need for power supply wires, but conventional batteries have a limited life. Thus, continual battery replacement becomes a major drawback, particularly in vehicle applications where a large number of switches are used. Thus, for applications such as automobiles and aircraft, a power source with at least a twenty-year life expectancy is required. As a consequence, a need exists for a wireless switch arrangement that does not require any external power distribution wiring while also being capable of attaining the desired twenty-year life expectancy.
It is therefore an object of the present invention to provide a wireless switch arrangement that generates its own electrical power to remove any need for a direct connection to a battery or other external source of electrical power.
It is another object of the present invention to provide a wireless switch having a local energy harvesting arrangement dedicated to the switch circuit to remove any need for an external power supply wire connection to the switch.
It is yet object of the present invention to provide a wireless switch having at least a twenty-year power source.
In accordance with these and other objects, the present invention provides a twenty-year life, self-powered wireless switch for automobiles, aircraft (e.g., jet engines), elevators, and other applications requiring transmission of control signals/information from an inaccessible or rotating location. The self-powered wireless switch is provided with a wireless transmitter, and an energy harvesting device arranged to produce electrical power for operation of the wireless transmitter when actuated by a switch. In accordance with aspect of the present invention, the energy harvesting device includes a piezoelectric element arranged to be distressed upon actuation of the switch. In accordance with another aspect, the energy harvesting device can include a tritium lamp arranged to energize a phosphor coating to produce light upon actuation of the switch, and at least one photo detector arranged to receive the light and generate the electrical power. In accordance with still another aspect of the present invention, the energy harvesting device includes at least one photo detector arranged to receive the light from a lamp. Preferably, the lamp can be arranged to generate black light.
Thus, the present invention provides a switch arrangement that can be located without regard to insuring accessability of a wiring harness or connector. This freedom to locate a switch anywhere without being confined by a wire harness reduces the complexity of the power distribution system in such applications as automobiles, aircraft and HVAC equipment.
Embodiments of the present invention comprehend a self-powered wireless switch comprising a wireless transmitter, an energy harvesting device, and an electric circuit. The energy harvesting device is arranged to produce electrical power for operation of the wireless transmitter upon actuation of a switch by a user. The energy harvesting device includes a piezoelectric element arranged to be distressed upon actuation of the switch. The electric circuit includes a matching wound step down transformer coupling the piezoelectric element to a rectifier connected to a capacitor. The electric circuit allows the piezoelectric element to resonate and the capacitor to receive the harvested energy and supply electrical power for operation of the wireless transmitter.
The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.